Currently, common active array liquid crystal displays typically use amorphous silicon thin film transistors (TFTs) and polysilicon thin film transistors.
A polysilicon thin film transistor has advantages of higher electron mobility, high aperture ratio, high response speed, the ability of scaling down the component size, high resolution, capability of forming integrated drive circuit and etc., therefore it is suitable for high-frequency display of large capacity, facilitates the yield of the display and cost reduction, and has various applications.
Generally, a low-temperature polysilicon thin film is formed by excimer laser annealing. The fundamental of the excimer laser annealing is to irradiate the surface of an amorphous silicon thin film so that the amorphous silicon is melt, cooled, re-crystallized and then converted into polysilicon. The low-temperature polysilicon thin film formed by excimer laser annealing has advantages of great grain, good space selectivity, and excellent electrical characteristic. The excimer laser annealing has become a predominant method for forming a low-temperature polysilicon thin film.
However, in the current technology, it is difficult to form a low-temperature polysilicon thin film having uniformity and great grains. Furthermore, because the incident laser light is reflected to a great extent, the energy of the incident laser light is wasted greatly, which is detrimental for realizing low cost production of the low-temperature polysilicon thin film and the improvement of the performance of the low-temperature polysilicon thin film.